Here in Canada, there were a number of choices last December (that's when my son was looking) at Future Shop. They seemed either expensive (same price or more than the Clip+) or poor looking. Fortunately, I didn't have to decide, and I never did find out what my son bought.

Lots of speakers out there that can be attached by an audio cable to the player's headphone jack, that are powered by battery and/or AC power (although not USB). Kind of a standard for most portable speakers. I still have my CD case-sized (but thicker) Sony portable speaker system that uses battery or AC power, with tweeters that twist to different directions for good spatial effect and that even has a mini-bass port. (The SRS-T77 -- no longer in production.)

It plugs into your headphone jack and then attaches to almost anything and turns it into a speaker. No I don't own one, nor have I seen one in real life, but the idea seems so neat. (It was $24 in a local store two weeks ago, but I decided to save my money. If it's under $20 after Xmas, I'll probably go to the store for a listen at least.)

Record some speech and attach to a pumpkin at Halloween, for a real Talking Head. OK OK I have some pretty weird ideas at times.

I didn't look at all of those but anything that allows you to connect via headphone jack should work fine.

+1,Exactly ,"anything" that "finishes" or can finish on a male jack / aux in /line in conector
works ok with any decent portable dap, even a hifi device as long as you switch
off&on the player when the hifi is mute or low at low volume (clipping&peaks can kill speakers, specially tweeters)
usually 3/4 of a headfhone out is close to line out level of Hi-Fi home devices

For a portable thing , i own& love this one:Creative D100:
Has AC/DC (4x1.5AAA) NOT usb but does have bluetooh(the clip obviously could only be connected to the jack, but on my cowon s9 syncs good) using it daily at shower low-end alkalines last over a month+
Well balanced sound , sounds like x2 price device an has NO distortion
It's a 2.0 device (Two full range speakers)with a rear bass reflex strucutre